Towards the Ultimate Control of Light: Optical frequency metrology and the phase control of femtosecond pulses

In just the past year there has arisen a remarkable convergence of two seemingly disparate subfields of optical physics: precision optical frequency metrology and ultrafast phenomena. The former field is typified by the variety of spectroscopic and fundamental physical measurements that can be made using a continuous wave (CW) laser best described by its near delta-function frequency spectrum. In sharp contrast, the field of ultrafast phenomena encompasses the study of sub-picosecond events using laser pulses that approach the limit of time domain delta-functions. In fact, at this time state-of-the-art laser sources from these two fields share nearly the same delta-function “figure of merit” with frequency and temporal widths on the order of a few parts in 1015 hertz and seconds, respectively. In this article, we will present relevant details of these two subfields, then explore their connection, and finally highlight the most recent advances made possible by this surprising union.